In some situations to investigate and solve email issues, email headers are needed. The email header is an HTML code that contains information about the sender, recipient, email’s route to get to the inbox, and various authentication details. 

To find email headers you should follow the below steps:

Webmail:

1. Open up a message by double-clicking on it;
2. Click on “Details”, and then on “All headers…”:

Google Gmail:

1. Open up a message by double-clicking on it
2. Press on section “More”, and then on “Show original”:

Microsoft Outlook 2007:

1. Open up a message by double-clicking on it;
2. Press on section “Message Options“, and then on “Internet Headers”.

Microsoft Outlook 2010, 2013, 2016, and 2019 (365):

1. Open up a message by double-clicking on it;
2. Click the “File” tab in the top left of the message;
3. Choose “Properties” from the bottom of the list and you’ll see “Internet Headers”.

Mozilla Thunderbird:

1. The first option to reach headers is: 

• Open up a message by double-clicking on it;
• Press the buttons Ctrl+U.

1. The second option to reach headers is:

• Open up a message by double-clicking on it;
• Select the section “View”, and then choose “Headers”:

An example of a simple header:

1. Return-path: <dmitrij***@gmail.com>

Envelope-to: [email protected]

Delivery-date: Fri, 20 Nov 2020 10:54:32 +0200

2. Received: from mail-lj1-x22a.google.com ([2a00:1450:4864:20::22a]:35934)

by lt4.eu.cpanel.hostens.cloud with esmtps (Exim 4.93)

(envelope-from <dmitrij***@gmail.com>)

id 1kg2Ba-0022sG-PZ

for [email protected]; Fri, 20 Nov 2020 10:54:32 +0200

3. Received: from (xx-56-76-xxx.static.zebra.lt. [xx.56.76.xxx])

From: Dmitrij Zzzz <dmitrij***@gmail.com>

Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.20.0.2.21\))

Subject: Headers

Message-Id: <[email protected]>

Date: Fri, 20 Nov 2020 10:53:48 +0200

To: [email protected]

Return-path: <dmitrij***@gmail.com>

Envelope-to: [email protected]

Delivery-date: Fri, 20 Nov 2020 10:54:32 +0200

Analyzing of provided header:

1.

• Return-path: <dmitrij***@gmail.com>

Returned sender address

• Envelope-to: [email protected]

Email sender’s address

• Delivery-date: Fri, 20 Nov 2020 10:54:32 +0200

The exact date of a delivered email (time zone depends on the use server’s settings)

2. 

• from mail-lj1-x22a.google.com ([2a00:1450:4864:20::22a]:35934)

Sender server’s hostname and IP address

•  by lt4.eu.cpanel.hostens.cloud with esmtps (Exim 4.93)

Recipient server’s hostname and name of installed mail service (Exim)

• id 1kg2Ba-0022sG-PZ

Unique message ID 

• for [email protected]; Fri, 20 Nov 2020 10:54:32 +0200

Email sender address and exact date of email sending

3. 

• Received: from (xx-56-76-xxx.static.zebra.lt. [xx.56.76.xxx])

Sender’s local IP address ()provided by ISP)

• From: Dmitrij Zzzz <dmitrij***@gmail.com>

Sender’s email address

• Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.20.0.2.21\))

Mail App thee email was sent from

• Message-Id: <[email protected]>

Unique message number intended for tracking email

Other specific details such as sending date, sender email address, recipient address, and delivery date.